New UPS

Guys,

I am thinking of buying a new Uninterrupted Power Supply.

This is the model I'm interested in : http://3btech.net/fe80liinupsb.html

My PC Specs are :
-> AMD 64 3200
-> ATi 9800 256
-> Mobo
-> 2 Hard Disks - 120 + 120
-> CD WR
-> DVD
-> LG Flatron 775FT (taking power from UPS ITSELF)
-> PSU Raidmax 450 W

You think this UPS is good enough for my specs? How much time you think it can give me ?

Thanks before hand for those who try to help me :)

Cheers